If a movie's merit were linked to the likability of its main character, "Rachel Getting Married" would rate a zero. Anne Hathaway's Kym, whose sister Rachel (Rosemarie DeWitt) is indeed getting married, is like a human Brillo pad. Recently out of rehab, she remains an emotional wreck. She is unable to shake her guilt over the accidental death of her little brother for which she alone holds herself responsible.

Kym is also deeply resentful of Rachel's impending nuptials, which, not entirely consciously, she attempts to undermine. In the film's most ghastly comic moment, Rachel suddenly announces to her family, in the middle of a fight with Kym, that she is pregnant. Instead of being happy for Rachel, Kym pouts. She regards the news as an unfair game-changing tactic in the sibling wars.

Hathaway has until now been known primarily as an ingénue, and so initially it's startling to see her acting all hopped up and abrasive. Clearly we are not in "Devil Wears Prada" territory. But we shouldn't make too much of this makeover. After all, it's standard operating procedure in Hollywood, particularly as Oscar season approaches, to go from squeaky clean to down and dirty. And Hathaway, adept as she often is here, tends to overdo it. Kym is pretty much a nonstop nervous wreck and director Jonathan Demme never lets us forget it. He keeps his camera trained on her with a relentlessness that would seem overweening even on "Cops."

If Demme had filmed in a more straightforward way, Hathaway, as well as many of the other performers, who also include Bill Irwin and Anna Deavere Smith, might have come across better. But he shoots almost everything on the go with a hand-held camera, and this gives the film a jiggliness that at times mimics the experience of being topside during a sea storm.

I don't know why directors think this approach confers "realism" on a movie. (Woody Allen made the same mistake in "Husbands and Wives.") Demme has had a successful parallel career as a documentary filmmaker, but even his documentaries (such as "Stop Making Sense") weren't as bobbly as this.

"Rachel Getting Married" is like a documentary in other ways, as well. The wedding sequence near the end suggests a concert jamboree – the groom (Tunde Adebimpe) is a musician – and for long stretches we seem to be witnessing a species of rock video. The music itself is marvelous, but it takes us away from the people. This is not altogether bad. As in an overwrought John Cassavetes movie, which "Rachel" sometimes resembles, there are times when we welcome being away from all the clawing and shouting.

Demme at his best, in films like "Melvin and Howard" and "Something Wild," has a wonderfully unstressed way of unveiling his characters. He lets the audience decide what to make of the people onscreen. This is also his strongest suit in "Rachel," although at times we might hope for a bit more psychological intricacy. Kym's family, for example, is white-bread New England WASP and yet nothing whatever is made of the fact that Rachel is marrying a black man. The racial egalitarianism of the situation is admirable but also a tad unrealistic. (The script is by Jenny Lumet, the daughter of director Sidney Lumet and granddaughter of Lena Horne. What a legacy!)

Few dramatic situations are more concentratedly powerful than weddings, as Demme well knows. In "Rachel," he extends the nuptials into disaster movie territory. Kym wreaks havoc with everybody, most of all with herself. Not all of her body blows hit home, but there is one scene near the end, when she physically confronts her mother, that resonates like a gong. I think the reason this scene is so powerful is because Debra Winger, who has been way too long absent from the big screen, plays the mother. With a minimum of actorly fuss, Winger shows us the rage and hurt inside this overcontrolled woman. It's a great piece of acting – high drama at the service of the highest talent. Grade: B (Rated R for language and brief sexuality.)